The invention relates generally to water screens and, more particularly, to traveling water screen systems with boot seals.
Water drawn into an industrial plant from a lake or river must be filtered to prevent debris from fouling equipment and causing damage. Traveling water screens are used to filter out and remove debris and fish from an influent channel before the debris can enter the plan or fish impinged on the upstream face of the screen die. A typical traveling water screen comprises a motor-driven screen, such as a foraminous conveyor belt, extending laterally across the width of the channel and vertically from the bottom of the channel to a height above the level of the water to ensure that all the water flowing in the channel passes through the screen. The screen travels a circuitous path around a motor-driven head shaft above the level of the water and a lower idle shaft in a boot section of the water screen at the bottom of the channel. The screen travels upward along the upstream portion of its circuitous path and downward along the downstream portion. A series of lift elements, such as baskets, scoops, or flights, extending outward of the screen at periodic intervals along its length lift debris or fish trapped on the upward-moving upstream portion of the water screen out of the channel for disposal in the case of debris and safe transit in the case of fish. Seals prevent unfiltered water containing fish and debris from flowing into the boot section of the water screen system between the screen and the bottom of the channel. One kind of seal, shown in FIG. 1, comprises an elastomeric or rubber flap 10 extending horizontally from a fastened end 11 at the bottom of the channel upstream of a water screen 14 to a free end 12 close to the upstream face 13 of the water screen in its boot section 15. A lift element 16 approaches the flap in a vertical direction 17 forming a 90° contact angle γ with the flap at the point of contact P. As the lift element moves past the flap, the flap flexes, its free end sliding along the tip 18 of the lift element to maintain the seal. Once the lift element passes, the flap returns to its unflexed, sealed position with its free end close to the upstream face of the screen. The flap must be flexible enough to bend almost 90° at its contact point to allow the lift element to pass. But, to provide an adequate seal and endure the continuous flexing, the flap must be fairly stiff and durable, which puts a lot of pressure on the lift elements as they pass. The repetitive contact between the flap and the lift elements wears or damages the lift elements and the flap and weakens or destroys the seal.